Our transcription: The late Paleozoic was a time of great global scale changes. It was during this time that almost all of the continents were tectonically assembled into a single supercontinent called "Pangea." This immense land mass nearly spanned the Earth from pole to pole forming a tremendous north to south barrier that blocked ocean circulation and severely disrupted the climate. The continental collisions that created Pangea also transformed continental margins from shallow seas rich with life into mountain ranges similar to the Alps and the Himalayas. These changes in climate and terrain in late Paleozoic time had a grave effect on the global ecosystem. It triggered the largest mass extinction in all of Earth history. In this tragic finale to a geologic era, over 90 percent of all known species of life disappeared.